1. Field of the Invention
This invention relates to an air intake manifold and method for assembly thereof where the intake manifold includes an internal fuel rail and wire harness that allows fuel injectors to be installed inside the manifold to form a subassembly.
2. Related Art
Internal combustion engines operate by burning a mixture of fuel and air in a cylinder containing a piston. Engine power is provided by a continuous cycle that takes place inside the engine. First, as the piston moves downward, an inlet valve opens and a mixture of fuel and air is sucked into the cylinder chamber. The valve closes and the piston moves up to compress the mixture. An electric spark plug produces a spark that ignites the fuel, forcing the piston back down. Finally, an outlet valve opens and the piston rises back up to release the exhaust gases out of the cylinder. The cycle continually repeats itself until the engine is shut down.
The engines use fuel injectors to control injection of fuel into the engine cylinders. An air intake manifold is fastened to the engine to provide a system of guides or runners that supply air to be combined with the fuel to form a mixture. The fuel injectors are cylindrical members that are typically mounted to a fuel rail. In most applications, the fuel rail is an external member that is fastened to the outside of the air intake manifold. The fuel injectors are received into bores formed along the manifold.
In some applications, the fuel rail is formed inside the manifold to eliminate attachment hardware and assembly cost. One such manifold is shown in U.S. Pat. No. 5,682,859 issued on Nov. 4, 1997 for "Method and Arrangement For Mounting Fuel Rails" and assigned to the assignee of the present invention. In this arrangement the fuel injector is separately installed externally to the manifold by installing one end of the injector for communication with the fuel rail with the other end of the injector installed into the runner for communication with the intake port for the cylinder. This mounting arrangement requires special seals and the assembly process can be difficult and time consuming. Further, since the fuel injectors are mounted outside of the manifold, the injectors are noisy and cause unwanted vibrations.
In some cases, the traditional mechanical linkage between the accelerator pedal and the engine throttle is replaced by electronic throttle control (ETC). In ETC configurations, an electric signal controls the position of the engine throttle and fuel supply therefor. Wiring harnesses are used to connect the fuel injectors to a power supply for the ETC system. Typically, these wiring harnesses are mounted externally to the manifold, thus exposing the harness to potential damage and environmental contaminants.
Thus, it is desirable to have a mounting arrangement for a fuel injector where the injector can be mounted inside a manifold that has an internal fuel rail to eliminate special mounting hardware and unwanted noise. Further it would be desirable to have such a manifold where wiring needed for electronic throttle control could be easily integrated into the manifold.